An example of prior art lancing device is disclosed in JP-A-11-9577. As shown in FIG. 16, the prior art device includes a generally cylindrical housing 90 and a lancet holder 92 arranged in the housing for holding a lancet L. A cylindrical plunger 93 is fitted into one end of the housing 90. In this prior art device, when the plunger 93 is pushed in the arrow N1 direction, the lancet holder 92, which has latched on a predetermined portion in the housing 90, is forced to be released from the latched state. As a result, the lancet holder 92 advances toward a tip end opening 90a of the housing 90 due to the resilient force of a spring 95. As shown in FIG. 16C, a tip end surface 90b of the housing 90 is pressed against skin 99, so that the advancing movement of the lancet holder 92 causes the tip end of the lancet L to stick into the skin 99.
The housing 90 comprises two sleeves 90A and 90B connected to each other. The sleeve 90A is movable relative to the sleeve 90B in the axial direction (arrow N2 direction) of the housing 90. Specifically, as shown in FIG. 16B, the sleeve 90A has an inner circumferential surface provided with an inclined surface 90c. When the sleeve 90A is rotated, the inclined surface 90c engages with a predetermined member, which allows positional adjustment of the sleeve 90A in the arrow N2 direction.
In such a structure, as shown in FIG. 16c, by adjusting the position of the sleeve 90A, it is possible to vary the dimension s1 of the lancet L projecting from the tip end surface 90b of the housing 90 when the lancet L is advanced toward the tip end of the housing 90. Therefore, the sticking amount of the lancet L relative to the skin 99 is variable.
However, the prior art device has the following problems.
When the tip end surface 90b of the housing 90 is pressed against the skin 99 with a small force, the skin 99 is generally flush with the tip end surface. However, as shown in FIG. 17, when the pressing force relative to the skin 99 is strong, the skin 99 enters the tip end opening 90a of the housing 90. The entering amount is not constant but varies depending on the softness of the skin 99. In sticking the lancet L, negative suction pressure may often be exerted on the portion to be stuck to cause bleeding from that portion. Also in such a case, the entering amount is not constant.
However, the prior art device described above can adjust only the dimension s1 of the lancet L projecting from the tip end surface 90b of the housing 90. Therefore, the sticking amount into the skin 99 by the lancet L differs between the case where the skin 99 is flush with the tip end surface 90b as shown in FIG. 16C and the case where the skin 99 enters the tip end opening 90a as shown in FIG. 17. Further, in the case where the skin 99 enters the tip end opening 90a, the sticking amount of the lancet L varies depending on the entering amount s2. Thus, with the prior art device, sticking of the lancet L into the skin just by an intended amount is difficult. As a result, due to excess or insufficient sticking amount of the lancet L, there have been such problems that the skin is hurt more than necessary or the amount of bleeding from the portion stuck by the lancet L is insufficient.